1. Field of the Invention
The present invention relates in general to an oxygen sensor for measuring the oxygen concentration in a fluid, and more particularly to an oxygen sensor unit which comprises a so-called flat film type oxygen sensor element and an element support by which the sensor element is supported.
2. Description of the Prior Art
Flat film type oxygen sensor elements, which employ a flat solid electrolyte layer, show better performance with regard to EMF (electromotive force) characteristics and responsiveness as compared with tubular type oxygen sensors which employ a soloid electrolyte in the form of a tube. However, some oxygen sensor elements of the flat film type fail to exhibit their maximum possible performance because of use of an element support having poor thermal insulating characteristics. In fact, the usage of such element support causes considerable heat release from the sensor element at its base thereby preventing the sensor element from being kept at an effective operating temperature. This phenomenon becomes more critical when the sensor is exposed to a fluid having relatively low temperatures.